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THE BASIC-BESSEMER PROCESS.
117
acid in the gases during the first stage of the operation arises from the chilling action of the basic additions, for at low temperatures carbonic acid is not readily reduced by carbon, but as the metal becomes hotter the carbon assumes more complete command and appears almost entirely in the form of carbonic oxide. At the end of the blow, when phosphorus is burning, the oxygen is held in the bath and the only gaseous product is the nitrogen, so that when the combustion of phosphorus is ended there is no such sudden change in the character of the flame as marks the death of the carbon reaction, and in order to be sure of the purity of the metal it is necessary to make fracture tests on small sample ingots before the charge is poured from the converter.
SEC. Vile.—Elimination of sulphur.—Sulphur is partly removed at the same time as the phosphorus, but, if in large quantity, it may be necessary to continue the blast after dephosphoriza-tion with the sacrifice of iron. This, however, is bad'practice, and is far from being economical or desirable. In a series of heats made by the Pennsylvania Steel Company, in 1883, a content of 0.25 per cent, was reduced below 0.05 per cent. Manganese was
TABLE VII-B.
Reduction of Manganese from Slag in the Basic Converter. (See Journal I. and B. 1., Vol. I, 1893', p. 63.)
Heat.	Time of taking test of metal.	Composition, per cent., of the metal in the bath.		
		Mn.	P.	8.
No. 184	Disappearance of spectrum, line, At second lime addition.	0.19 0.62	2.070 0.468	0.133 0.067
No. 185	Disappearance of spectrum line, At second lime addition,	0.24 0.81	2.180 0.718	0.072 0.042 '
No. 186	Disappearance of spectrum line, At second lime addition,	0.24 0.79	2.890 0.483	0.081 0.047
present up to about 2,0 per cent., and this aids in the work, probably by the formation of sulphide of manganese. Even after the manganese has entered the slag it may be available for this function, for it can be reduced by the phosphorus and incorporated into the metal. Table VII-B is from ,a paper by Stead* to show the
* On the Elimination of Sulphur from Iron.  Journal I. and S. L, Vol. 1,1893, p, 61,-